Measuring device and method for measuring a seat mat for a vehicle seat

ABSTRACT

A measurement apparatus and a method for measuring a seat mat for a vehicle seat which serve to perform a function test or a recording of readings by way of a negative pressure that is generated in the seat mat. The negative pressure is established by way of a pressure difference between the negative pressure and the external atmospheric pressure. The method is thus independent of the external atmospheric pressure. The controller that establishes the pressure difference is embodied either electronically or mechanically.

FIELD OF THE INVENTION

The present invention is based on a measurement apparatus and a methodfor measuring a seat mat for a vehicle seat.

BACKGROUND INFORMATION

It is already known that seat mats for a vehicle seat are measured, interms of their function and in order to record readings, either with aplunger having a defined weight or in an overpressure chamber. Theplunger has a specific weight, for example 400 g, while in the case ofthe overpressure chamber, a variety of readings can be generated bymodifying the overpressure in a pressure chamber. The pressure chamberis approximately the same size as the scat mat, and is suitable forresisting a defined overpressure.

SUMMARY OF THE INVENTION

The measurement apparatus and method according to the present inventionfor measuring a seat mat for a vehicle seat have, in contrast, theadvantage that because a negative pressure is used in the seat mat, aneasily adjustable pressure difference between the external atmosphericpressure and the aforesaid negative pressure results in an accuratesetting for the weight load. In particular, the method and measurementapparatus according to the present invention are thus independent of theexternal atmospheric pressure, since in fact only the difference is usedto set the negative pressure.

The fact that a negative pressure is used in the seat mat makes themethod according to the present invention safer, since there is no needfor an overpressure chamber that can burst as a result of anuncontrolled overpressure. Since a pressure chamber is not necessary,the measurement apparatus according to the present invention canadvantageously be placed along with the seat mat in an environmentalchamber, in order to perform a temperature-dependent measurement.Because of the fact that an overpressure chamber is not required for theseat mat, the measurement apparatus is easily transportable and thuseasy to handle.

It is particularly advantageous that the controller is embodiedelectronically, thus making automation possible. A mechanical embodimentof the controller results in flexible handling of the method accordingto the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic depiction of the seat mat in cross section, withthe measurement apparatus connected.

FIG. 2 is a block diagram of the seat mat and the connected measurementapparatus with analysis system.

FIG. 3 shows the method according to the present invention as a flowchart.

DETAILED DESCRIPTION

Seat mats for vehicle seats have pressure-dependent resistors, forexample in order to indicate to a restraint system in a vehicle who orwhat is sitting on the respective seat. This makes possible, inparticular, a classification of persons (height and weight) and adifferentiation between persons and objects. Seat profiles, inparticular, are also used for this purpose.

The pressure-dependent resistors are so-called FSR (force sensingresistor) sensors. The FSR sensors are made up of two substrates ontowhich pressure-sensitive films and electrodes are applied. When a forceis exerted on this FSR sensor, its electrical resistance decreases. Thisdecrease is a monotonic function of the applied force. Several sensors,whose resistance values are measured and converted into digital values,are housed in a seat mat.

After the mats are manufactured, a functional test or instrumentalcharacterization of the sensors in the seat mat is preformed. A methodand measurement apparatus for measuring the seat mat for a vehicle seatwhich use a negative pressure in the seat are therefore utilizedaccording to the present invention, a pressure difference beingestablished between that negative pressure and the atmospheric pressureof the environment. This pressure difference is controlled by acontroller that is embodied either electronically or mechanically. Thereadings are indicated as a function of the applied pressure produced bythe negative pressure.

FIG. 1 schematically depicts a cross section of a seat mat with ameasurement apparatus according to the present invention connected toit. The seat mat has a film 1, a plastic layer 2 as spacer, and a secondfilm 3, FSR sensors 4 being adhesively bonded onto films 1 and 3. Inaddition, electrodes and conductors (not depicted here) are applied ontofilms 1 and 3 in order to sense the readings of FSR sensors 4. Cavities6 are present in the seat mat to allow an elastic reaction to an appliedpressure. Since the air in cavities 6 is intended to escape when aweight is present on the vehicle seat having the seat mat, to allow anelastic reaction to that pressure the seat mat includes a ventingconduit 7 to which the measurement apparatus according to the presentinvention is connected.

A suction connector 5 is therefore mounted on the seat mat via ventingconduit 7. Connected to suction connector 5 at the other end is a pump 9that, by way of a controller 8, controls in terms of the pressuredifference between the negative pressure in the seat mat and theexternal atmospheric pressure. Controller 8 measures the vacuum and theexternal atmospheric pressure, and controls the pump in accordance witha value set on controller 8. Controller 8 is here arranged betweensuction connector 5 and pump 9. Arrows 20 and 21 indicate the force ofthe external atmospheric pressure that acts when a negative pressure isgenerated in the seat mat. The recording apparatus for the readings ofFSR sensors 4, and the memory and output apparatus connected to therecording apparatus, are not depicted here.

The measured readings are converted into weight values using a storedtable that is then located in a control unit in the vehicle. From thosevalues, a processor in the control unit can then calculate how heavy andtall the person will be, the seat profile additionally being used. Thisis performed for adjustment of an airbag in order to prevent injury topersons upon triggering of an airbag.

FIG. 2 shows the seat mat with the connected measurement apparatus as ablock diagram. A seat mat 10 is pumped down by way of the pump togetherwith a controller and a suction connector, combined into block 14, inorder thereby to generate a negative pressure in seat mat 10.

Electrical terminals of seat mat 10 lead to a recording apparatus 11 forthe readings. A first data output of recording apparatus 11 for thereadings leads to a display 12, and a second data output of recordingapparatus 11 leads to a memory 13.

The regulated pump unit 14 pumps seat mat 10 down in order to generatethe negative pressure, the negative pressure being established by apressure difference between the negative pressure and the externalatmospheric pressure. As a function of this pressure difference, FSRsensors 4 in scat mat 10 yield different resistance values that aremeasured by recording apparatus 11. For that purpose, recordingapparatus 11 applies a voltage to the electrical terminal of electricalseat mat 10, or it drives a current through the electrical terminal, inorder ultimately to ascertain the resistance of seat mat 10. Theseresistance values are then digitized and optionally further processed inrecording apparatus 11 in order then to display the values by display 12and/or store them in memory 13.

It is furthermore possible for a curve tracer to be connected torecording apparatus 11 so that the measured resistance values of FSRsensors 4 can be outputted directly as a function of the pressuredifference that is generated. This furnishes a test of the functionalityof seat mat 10. The measurement apparatus according to the presentinvention is therefore made up of suction connector 5, pump 9,controller 8, recording apparatus 11, display 12, and memory 13.

If the characteristic curve is to be outputted as a function of thepressure difference, a connection between controller 8 and recordingapparatus 11 is provided.

FIG. 3 depicts, as a flow chart, the method according to the presentinvention for measuring seat mat 10 for a vehicle seat. In method step15, the measurement apparatus according to the present invention isconnected to seat mat 10. In method step 16, a pressure differencebetween the interior of seat mat 10 and the external atmosphericpressure is established by suction connector 5, pump 9, and controller8, a negative pressure being generated in seat mat 10. For that purpose,the regulated pump unit 14 pumps the air conduits of seat mat 10 untilempty.

In method step 17, this pressure difference is therefore established,and then in method step 18 the corresponding readings are recorded byrecording apparatus 11 and optionally displayed with display 11 orstored in memory 13 for later processing. In method step 19, this outputof the characteristic curve is performed.

It is furthermore possible for the measurement apparatus according tothe present invention to be transported, with seat mat 10, into anenvironmental (climatic) chamber 22 (FIG. 2) so that atemperature-dependent measurement can be performed therein.

1. A measurement apparatus for measuring a seat mat of a vehicle seat,the seat mat including two films provided with pressure sensors betweenwhich at least one cavity is present, a plastic layer arranged betweenthe two films, and a venting conduit, the measurement apparatuscomprising: a suction connector for connection to the venting conduit; apump for generating a negative pressure in the seat mat; a controllerfor establishing a pressure difference between the negative pressure inthe seat mat and an external air pressure; a recording apparatus forreading the pressure sensors; and an arrangement for at least one ofoptically outputting a reading of the pressure sensors and storing thereading.
 2. The measurement apparatus according to claim 1, wherein: thecontroller includes an electronic controller.
 3. The measurementapparatus according to claim 1, wherein: the controller includes amechanical controller.
 4. A method for measuring a seat mat for avehicle seat, comprising: exposing the seat mat to a pressure load forat least one of: i) performing a recording of a reading, and ii)performing a function test; establishing a negative pressure in the seatmat in order to generate a pressure load; and controlling a pressuredifference in the seat mat between the negative pressure in the seat matand an air pressure in an environment.
 5. The method according to claim4, wherein: the measurement of the seat mat is performed in a climaticchamber.
 6. The method according to claim 4, wherein: the pressuredifference is controlled electronically.
 7. The method according toclaim 4, wherein: the pressure difference is controlled mechanically.